The present invention relates generally to the field of offshore structures for the exploration and production of mineral resources (e.g., petroleum and natural gas) from the seabed. More particularly, the present invention relates to the type of structure commonly referred to as a “gravity-based structure” or “GBS,” and specifically it relates to a system for stabilizing such structures against lateral shear forces, for example, of the type exerted by strong wave action during storms.
Gravity-based structures, as exemplified in U.S. Pat. No. 4,265,568, are suitable for use in relatively shallow bodies of water, where it is practical to anchor the bottom (keel) of the GBS to caissons embedded in the seabed. In such shallow water applications, the GBS is sometimes subjected to very strong lateral shear forces exerted by wave action during storms. To stabilize the GBS against such shear forces, shear skirts are provided around the keel. In some installations (e.g., in areas of unconsolidated clay seabed), the shear skirts may have a height of about 10 meters or more, requiring a deep graving dock for fabrication and float-out of the GBS. Thus, the need for tall shear skirts increases the costs of fabricating and installing the GBS.
It would thus be advantageous to provide a mechanism for stabilizing a GBS against lateral shear forces that does not require the use of shear skirts.